The proposed studies are designed to uncover information about the mechanisms controlling the biosynthesis, transport, storage, and release of bioactive peptides produced in neurosecretory systems. The primary approach involves studies on organ culture and tissue culture preparations which contain functioning neurosecretory systems. By using to advantage the efficiency with which such cultured systems can utilize radio-labelled amino acid tracers, it is possible to simultaneously make observations about the various stages of the neurosecretory process described above. The systems being studied are the guinea pig hypothalamo-neurohypophysical complex, the rat and guinea pig pineal gland, and the teleost caudal neurosecretory system.